<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		
		<form action="">
			
			<input type="text" placeholder="表单内容不能为空" required />
			
			<input type="text" pattern="\d\d\d\d"  />
			
			<br /><br />
			<input type="submit" />
		</form>
		
		
	</body>
</html>
